Supplementary Bug Fixes vs. Re-opened Bugs

A typical bug fixing cycle involves the reporting of a bug, the triaging of the report, the production and verification of a fix, and the closing of the bug. However, previous work has studied two phenomena where more than one fix are associated with the same bug report. The first one is the case where developers re-open a previously fixed bug in the bug repository (sometimes even multiple times) to provide a new bug fix that replace a previous fix, whereas the second one is the case where multiple commits in the version control system contribute to the same bug report ("supplementary bug fixes"). Even though both phenomena seem related, they have never been studied together, i.e., are supplementary fixes a subset of re-opened bugs or the other way around? This paper investigates the interplay between both phenomena in five open source software projects: Mozilla, Net beans, Eclipse JDT Core, Eclipse Platform SWT, and Web Kit. We found that re-opened bugs account for between 21.6% and 33.8% of all supplementary fixes. However, 33% to 57.5% of re-opened bugs had only one commit associated, which means that the original bug report was prematurely closed instead of fixed incorrectly. Furthermore, we constructed predictive models for re-opened bugs using historical information about supplementary bug fixes with a precision between 72.2% and 97%, as well as a recall between 47.7% and 65.3%. Software researchers and practitioners who are mining data repositories can use our approach to identify potential failures of their bug fixes and the re-opening of bug reports.